Current orthodontic treatment with orthodontic brackets or other devices that may be attached to the patient's teeth may require the enamel to be prepared prior to attachment of the device to the tooth. Preparation of the tooth surface may be through a series of steps including cleaning, acid etching, and sealing, with intermediate rinse and dry steps, before the clinician may apply an adhesive. For example, to bond a bracket to tooth enamel, each tooth is first cleaned with a slurry of abrasive, such as pumice, to remove pellicle from the enamel. Then, after rinsing and drying the cleaned surface, a phosphoric acid etchant is carefully placed on the surface locations of the tooth to which the clinician desires to attach the orthodontic device. The acid etching step demineralizes the enamel surface and removes a layer of approximately 30 μm or so of hydroxyapatite from the enamel rods. After between 30 and 90 seconds of etch time, the etchant is rinsed away with a water spray and a high flow evacuator. In this way, etching provides a porous structure.
Following the drying step after etching, a sealant (e.g., Ortho Solo™ sealant) is applied to the etched surface. The sealant may penetrate the porous, acid etched surface. Once the sealant cures, a mechanical interlock is created between the tooth and the sealant. An adhesive (e.g., Enlight) and the bracket may be pressed onto the sealed surface with the adhesive between the bracket and the sealant. The adhesive may be a composite resin paste adhesive that includes a mixture of methacrylate monomers, a photo-initiator, and a glass/hydroxyapatite powder. Once the adhesive cures, it secures the bracket to the sealant. This bonding arrangement results in a sandwich-like construction with the sealant and the adhesive sandwiched between the tooth surface and the orthodontic bracket. This procedure and bonding arrangement is then repeated for each tooth that will receive an orthodontic device and so, in the case of orthodontic brackets and molar tube, this may involve 28 teeth per patient.
The current preparation process has many drawbacks. From the perspective of the clinician, it is a manually time-intensive process. It is not surprising that office chair time during the entire bonding procedure is lengthy. Overall, bonding orthodontic brackets to teeth is costly. From the patient's perspective, the process is uncomfortable and enamel removal is often irreversible due to the difficulty of remineralizing dental hard tissues. Thus, the tooth surface may be permanently compromised by acid etching. Certain patients may have an allergic reaction to the etchant. Liquid etchant may flow to the gingiva where it may irritate the soft tissue. Gel etchant, despite allowing more precise placement, requires skillful application and is more difficult to remove. In either application, when the etchant must be rinsed away, care must be taken not to splash or wash the etchant in a manner that may harm the patient or clinician, but the rinsing must be thorough so that the etching reaction is terminated and there is no residual acid or mineral debris that hinders the mechanical interlock between the tooth and the device.
During treatment, the decalcification of the enamel surface adjacent to fixed orthodontic appliances is prevalent. Decalcification is manifested as a white spot lesion (WSL). If left untreated, WSL may progress to produce carious cavitations, and may also present aesthetic problems. Thus, the prevention, diagnosis, and treatment of WSLs is crucial to minimize tooth decay as well as tooth discoloration that could compromise the aesthetics of the patient's smile. However, the problems and costs don't end with bonding.
After orthodontic treatment is complete, the clinician must remove the orthodontic bracket from each tooth. This debonding process requires the clinician to break the bond formed during the bonding process. Mechanically fracturing the bond may require significant skill on the part of the clinician if the patient is to avoid pain. Even with orthodontic brackets that include design features for easier debonding, considerable adhesive/sealant residue may be left on the tooth surface after removal of the bracket. This residue must be mechanically removed with a dental bur, which is an extremely uncomfortable process for the patient and is tedious for the clinician.
Therefore, a need exists for orthodontic adhesives, adhesive systems, and methods of using those adhesives and systems, that do not require the complex pre-attachment treatment described above and that reduce issues associated with debonding orthodontic devices from teeth.